String#count options

Question

From the documentation for String#count I understand the first example, but I do not understand the rest of the examples:

a = \"hello world\"
a.count \"lo\"              


        

Answer 1

Each argument defines a set of characters. The intersection of those sets determines the overall set that count uses to compute a tally.

a = "hello world"

a.count "lo"            # l o       => 5
a.count "lo", "o"       # o         => 2

And ^ can be used for negation (all letters in hello, except l)

a.count "hello", "^l"   # h e o     => 4

Ranges can be defined with -:

a.count "ej-m"          # e j k l m => 4